| Brassinosteroid(BR),as an important steroid natural plant hormone,has an important physiological role in various processes of plant growth and development and stress resistance.And it holds the characteristics of trace,high efficiency,non-toxic,etc.,so it has a high potential role in agriculture to improve plant related traits.However,the molecular mechanism of BR in affecting fruit development and coloration is currently unclear.In this study,the light-dependent purple eggplant " sanyueqie " was used as the experimental material,and the BR-deficient transgenic eggplant plants were obtained by heteromerous over expression of the Gh PAG1 gene.Gh PAG1 is highly homologous to P450 monooxygenase CYP734A1 / BUS1.Elucidate the molecular mechanism of BR regulating fruit development and anthocyanin accumulation from the transcription level and metabolic level.The main findings are as follows:1)Through genetic transformation mediated by Agrobacterium,endogenous BRdeficient transgenic plants were obtained.Compared with the wild type,the lack of BR resulted in dwarf plants,shrunken and curled leaves,dark green,reduced leaf inclination angle,reduced apical dominance,low fruit setting rate,delayed fruit development,and the entire plant growth cycle was delayed.In addition,peel coloring is reduced,the chlorophyll content is increased,and the chlorogenic acid content is increased.2)By exogenously spraying BR,the phenotype of BR-deficient plants was restored.It was found that after spraying BR of 200 n M and 700 n M,the plant height and leaf angle of the transgenic plants gradually increased and approached WT.3)Through analysis of RNA-seq data,it was found that 459 differential genes were detected when endogenous brassinolide accumulation was insufficient.According to functions,GO function enrichment is divided into three major categories: biological processes,cellular components,and molecular functions,and further divided into 21 functional groups.KEGG enrichment pathway analysis found significant enrichment in pathways such as plant hormone signal transduction,flavonoid biosynthesis,brassinolide biosynthesis,and plant pathogenic bacteria interaction.Compared with wild-type fruits,BR biosynthesis genes were significantly up-regulated and signal transduction genes were significantly down-regulated,and the expression levels of genes related to IAA,ABA,JA and SA signal transduction showed an overall downward trend.The expression level of anthocyanin biosynthesis genes in response to plant defenses and changes significantly decreased.These results explain the possible mechanism by which BR regulates fruit development and anthocyanin accumulation from the m RNA level.4)Through the analysis of multiple reaction detection mode of triple quadrupole mass spectrometry,it was found that the content of auxin,jasmonic acid,methyl jasmonate and salicylic acid decreased.The most significant change was jasmonic acid,followed by auxin.5)Through the use of UHPLC-Q-Orbitrap-MS technology for metabolite detection of transgenic and wild-type peel,a total of 214 different metabolites were detected and were divided into 29 categories.Then the principal component analysis of the sample is carried out,and a total of two principal components are obtained,which can explain 55.4% of the data model.After statistical analysis of differential metabolites,it was found that amino acids and their derivatives had the most types,with a total of 36 kinds.Followed by 31 flavonoids.Compared with the wild-type,the flavonoids in the transgenic peel mostly showed a downward trend.In summary,the absence of brassinosteroid caused a balance reset of various plant endogenous hormones,which affected plant growth and fruit development.In addition,BR mainly regulates anthocyanin biosynthesis by affecting jasmonic acid signal transduction,and ultimately affects anthocyanin accumulation. |
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